The present invention relates to a transmission unit for a vehicle with a transverse engine and gearbox mounted alongside the engine, in which the half-shafts transmit drive to the driving wheels of the vehicle. The half shafts have the same length, with one of the said half-shafts receiving drive from the differential through an intermediate shaft provided with a fixed support beneath the engine.
It is known that on modern front wheel drive vehicles with a transverse engine and gearbox, the differential is supported directly on the casing of the bearbox in a lateral position with respect to the central longitudinal plane of the vehicle. Therefore, some types of motor vehicle have half-shafts which transmit driving force from the differential to the driving wheels of the vehicle that are of different lengths. This asymmetry of the final elements of the transmission unit can produce disadvantages in running and vibrations, and may reduce the road holding ability of the vehicle due to the different elastodynamic characteristics of the two half-shafts of different lengths. To overcome this disadvantage, which is entirely negligible on motor vehicles of small capacity (about 1000 cc) but which can create very considerable problems on vehicles of high capacity and/or sporting vehicles, there are known transmission units in which the differential is provided on the side facing the mid line of the vehicle with an intermediate transmission shaft which extends to the opposite side of the vehicle where it is supported by means of a rigid support. In this way, the vehicle can be provided with half-shafts of identical length, one of which will be connected to the differential whilst the other is connected to the free end of the intermediate shaft. Transmission units of this second type are, however, of relatively high cost, due for the most part to the rigid support which must be formed and mounted with very great care in such a way as to avoid dangerous misalignments between the axis of the support and that of the intermediate shaft. Any misalignment would cause vibrations and an accelerated fatigue of the bearings which support the intermediate shaft. Finally, the thermal expansion and elastic deformation of the power unit during running can cause supplementary constraint or force loads. For this reason the assembly of such a transmission unit is also relatively time consuming and difficult.